Student Activity 8 D: Macroinvertebrate Metric Calculation ...



Student Activity 8 D: Macroinvertebrate Metric Calculation Sheet

Metrics are a numerical representation of the macroinvertebrate community. Each metric is like a snap shot of a particular component of the ecology of these organisms. All of the metrics together provide a complete picture of the stream system. Metrics provide the aquatic ecologists with numbers which are used in comparison studies such as bioassessment.

Instructions: Your task is to calculate the following metrics for your sample date. All of the numbers used in the calculations are found on the Macroinvertebrate Survey Data Sheet. Follow the directions under the title of each metric. Your task is complete when all of the metric values have been calculated.

Stream name:_     _____ Collection date:_     ___________

|1. Total number of organisms: |

|Count the number of individual organisms identified =      |

|2. Taxa Richness: Count the number of different types of organisms identified.=    |

|3. EPT Index: Add the number of different types of organisms belonging to the 3 orders: Ephemeroptera (mayflies), Plecoptera |

|(stoneflies), and Trichoptera (caddisflies) together. |

| |

|(# of E types =    )+ (# of P types=   )+(# of T types=   ) = EPT index=    _____ |

|4. Scraper : Collector-filterer ratio: |

|A. Count the # of scraper individuals and the # of c. filterer individuals identified. |

| |

|# of scraper individuals=     ___ # of c. filterer individuals=     _____ |

| |

|Divide the number of scrapers by the number of c. filterers. If a 0 appears in either the numerator or denominator, write the metric as a |

|fraction (0/# or #/0). |

|# of scrapers/ |

|# of c. filterers =Scraper:Collector filterer ratio=      |

|5. EPT : Chironomidae ratio: |

|A. Add the number of individual organisms belonging to the 3 orders: Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera |

|(caddisflies) together. |

| |

|(# of E ind. =     )+ (# of P ind.=    )+(# of T ind. =    ) E+P+T ind. total =      |

| |

|B. Divide the total in part A by the number of chironomidae collected. If a 0 appears in either the numerator or denominator, write the |

|metric as a fraction (0/# or #/0). |

|E+P+T ind. Total/ |

|# of Chironomidae = EPT:Chironomidae ratio=      |

|6. Percent Contribution of the Dominant family: |

|A. Record the family with the greatest number of individuals and the number of that family identified. |

| |

|Dominant family name:      |

|# collected in dominant family=      |

| |

|B. Calculate the percent contribution of this family by dividing the number of individuals from this family by the total number of |

|organisms collected in the sample and multiply by 100%. |

| |

| |

|# collected in dominant family |

|# collected in the entire sample = Contribution of |

| |

|X(100%) = dominant family=     % |

| |

|What is the tolerance value of this family? T =  __ |

| |

|What is the feeding group of this family? Feeding group =      |

|7. Hilsenhoff Biotic Index (modified to the family level) HBI: |

|A. Add all of the HBI values together. |

| |

|Total of all HBI values=      |

| |

|B. Divide the total in part A by the total # of organisms collected in the entire sample. |

| |

|Total of HBI values = |

|# collected in the entire sample = HBI (mod.)=      |

|8. Community balance: |

|A. Divide the total number of organisms belonging to each of the orders below by the total number of organisms identified in the sample |

|and multiply by 100%. |

| |

|# of organisms in each order = |

|# collected in the entire sample= X 100% |

| |

|Ephemeroptera (mayflies) =    % Diptera (true flies) =    % |

| |

|Plecoptera (stoneflies) =    % Coleoptera (beetles) =    % |

| |

|Trichoptera (caddisflies) =    % Megaloptera (dobsonflies) =    % |

| |

|Odonata (dragonflies & damselflies) =     % |

| |

|Non-insect macroinvertebrates =     % |

| |

|B. Using the percentages calculated above, make a pie chart which shows the approximate distribution of the benthic community found at |

|your study site. |

Student Activity 8 E: Bioassessment Calculation Sheet

Bioassessment is a scientific method used to compare the benthic community of a study stream to the benthic community of a reference stream. The results of a bioassessment are used to evaluate water quality.

Instructions: Your task is to determine the water quality of your study stream. You will be comparing the metrics calculated for your study stream to the metrics from a known high quality stream (reference site). The final result is a statement about the level of biological impairment. Follow the directions for each section.

Stream name:___      Collection date:     

Step 1. Copy the metrics for the appropriate reference stream (see last page) and the metrics for the study stream (see Student Activity 8 D: Macroinvertebrate metric calculation sheet) into the appropriate boxes below.

Be sure to use the data for the appropriate season (fall or spring).

Metric values from student activity 8D and the last page of 8E (reference site data)

|Metric |reference stream |site 1 |site 2 |site 3 |site 4 |

|Taxa richness |      |      |      |      |      |

|EPT Index |      |      |      |      |      |

|Scraper:c. filterer ratio* |      |      |      |      |      |

|EPT:Chironomidae ratio* |      |      |      |      |      |

|Contribution of the dominant | | | | | |

|family |     % |     % |     % |     % |     % |

|HBI(modified) |      |      |      |      |      |

* if a 0 occurs in the numerator the metric value = 0. If a 0 occurs in the denominator the metric value is undefined (in this case the metric is not used in further calculations).

Step 2. Calculate percent similarity of the study site metrics to the reference site metrics.

Instructions:

Part a: For the first 4 metrics "taxa richness, ept index, scraper/collector-filterer ratio, and ept/chironomidae ratio", divide the metric for the study stream by the metric for the reference stream and multiply by 100%. Write the % in the appropriate box.

Formula = (study site metric value / reference site metric value) X 100%

Part b: For "Contribution of the dominant family", copy the corresponding values from the table in step 1 into the appropriate boxes below.

Part c: For "HBI (modified)", divide the reference stream value by the study stream value and multiply by 100%. Write the % in the appropriate box.

Formula = (reference site value / study site value) X 100%

Results from step 2

|Metric |reference stream |site 1 |site 2 |site 3 |site 4 |

|Taxa richness |100% |     % |     % |     % |     % |

|EPT Index |100% |     % |     % |     % |     % |

|Scraper:C. Filterer ratio* |100%* |     % |     % |     % |     % |

|EPT:Chironomidae ratio* |100%* |     % |     % |     % |     % |

|Contribution of the dominant |      % |     % |     % |     % |     % |

|family | | | | | |

|HBI(modified) |100% |     % |     % |     % |     % |

*If either of these metrics had an undefined value in step 1 they are not used in further comparisons. Please cross out the appropriate boxes.

Step 3. Award 6, 4, 2, or 0 points to each percentage.

Use the point value table below to assign a point value to the percent values calculated in step 2. Write the corresponding point value in the appropriate metric point box below.

Percent ranges and corresponding point values

|Metric |6 points |4 points |2 points |0 points |

|Taxa richness |> 80 % |60 % to 79% |40 % to 59% |< 39 % |

|EPT index |> 90 % |80 % to 89% |70 % to 79% |< 69 % |

|Scraper : C. filterer ratio |> 50 % |35% to 49% |20 % to 34% |< 19 % |

|EPT : Chironomidae ratio |> 75 % |50 % to 74% |25 % to 49% |< 24 % |

|Contribution of the dominant |< 20 % |21 % to 30% |31 % to 40% |> 41 % |

|family | | | | |

|HBI (modified) |> 85 % |70 % to 84% |55 % to 69% |< 54 % |

Metric Point Box (Results from step #3) Note: The reference site will always score 6 points for each metric except “Contribution of the Dominant Family” Which will vary depending on the % recorded in Step 2.

|Metric |reference |site 1 |site 2 |site 3 |site 4 |

|Taxa richness |6 |      |      |      |      |

|EPT Index |6 |      |      |      |      |

|Scraper:C. Filterer ratio* |6* |      |      |      |      |

|EPT:Chironomidae ratio* |6* |      |      |      |      |

|Contribution of the dominant |      |      |      |      |      |

|family | | | | | |

|HBI(modified) |6 |      |      |      |      |

*If either of these metrics had an undefined value in step 1 they are not used in further comparisons. Please cross out the appropriate boxes.

Step 4. Add the points for each stream and write the total in the appropriate box.

Results of point totals

|reference stream =      |site 1=      |site 2=      |site 3=      |site 4=      |

Step 5. Divide the total points for the study site(s) by the total points for the reference site and multiply by 100%. Write the % in the appropriate box below.

Formula = (total points from study site / total points from reference site) X 100%

Results of comparison to reference stream points

|reference stream =100% |site 1=      % |site 2=     % |site 3=     % |site 4=     % |

Step 6. Draw conclusions about the benthic community and water quality.

Based on the result of step 5, use the following table to determine the level of impairment and water quality for the study site(s) and write the conclusions in the appropriate boxes on the following page. Also note if your score was high or low for the range (ex. 77% = high in the slightly impaired range)

Bioassessment criteria (modified from Rapid Bioassessment Protocols, Plafkin et. al 1989)

|% Comparison to Reference |Condition |Water quality |Attributes |

|Greater than 83% |Non-impaired |Excellent |Comparable to the best situation to be expected in that|

| | | |major basin. Optimum community structure and balanced |

| | | |trophic assemblage for that stream size and habitat. |

|54-79% |Slightly impaired |Very good to good |Community structure less than expected. Loss of some |

| | | |of the intolerant families. Percent of tolerant forms |

| | | |increasing. |

|21-50% |Moderately impaired |fair to poor |Fewer families due to a loss of most of the intolerant |

| | | |families. Reduction of the EPT index. |

|Less than 21% |Severely impaired |poor to very poor |Few families present. If there are high densities of |

| | | |organisms it is by a few tolerant families |

Results of bioassessment calculations

|Parameter |Reference |site 1 |site 2 |site 3 |site 4 |

|Bioassessment |non-impaired |      |      |      |      |

| | | | | | |

|Water Quality |excellent |      |      |      |      |

| | | | | | |

Reference stream data: The following 2 tables are data for the state reference streams.

1.) Select comparison data for the appropriate season (fall or spring).

2.) Select the stream which is located in the same major basin as your study stream.

3. Copy the metrics into the reference stream column in the table in step 1.

UPDATED METRIC VALUES (data from 1999-2004)

Fall data

|Metric |6000's |4000's |3000's |5000 &2000's |7000's |

| |Shepaug River |Salmon River |Natchaug River |Eightmile River |Saugatuck River |

|Taxa richness |18 |20 |24 |20 |15 |

|EPT index |10 |15 |16 |11 |9 |

|Scraper : C. filterer |0.971 |5.04 |1.09 |0.797 |0.22 |

|ratio | | | | | |

|EPT : Chiron. ratio |8.0 |7.84 |20.57 |11.091 |90.5 |

|Contribution of the |22.86 % |29.7% |21.4 % |21.2 % |38.3% |

|dom. family | | | | | |

|HBI(modified) |3.32 |2.64 |3.12 |3.33 |3.14 |

Spring data

|Metric |6000's |4000's |3000's |5000&2000's |7000's |

| |Shepaug River |Salmon River |Natchaug River |Eightmile River |Saugatuck River |

|Taxa richness |17 |22 |26 |16 |21 |

|EPT index |11 |15 |16 |9 |13 |

|Scraper : C. filterer |1.50 |5.00 |2.94 |0.132 |1.42 |

|ratio | | | | | |

|EPT : Chiron. ratio |15.333 |9.71 |7.11 |10.85 |1.72 |

|Contribution of the |20 % |24.6% |21.1% |30.36 % |24.49% |

|dom. family | | | | | |

|HBI(modified) |3.32 |2.52 |3.43 |3.22 |3.94 |

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